Sidelink positioning based on physical ranging signals

ABSTRACT

A user equipment (UE) in a vehicle (V-UE) broadcasts multi-phased ranging signals with which other entities may determine the range to the V-UE. The multi-phased ranging signals may include a first message, which may be broadcast in the Intelligent Transport System (ITS) spectrum, includes ranging information, such as a source identifier, location information for the broadcasting V-UE, and an expected time of broadcast of the ranging signal. The ranging signal may then be broadcast at the expected time and may include the source identifier. A second message, which be broadcast in the ITS spectrum, may include clock error information for the V-UE. A receiving entity may determine the range to the V-UE based on the time of arrival of the ranging signal and the expected time of transmission, as well as the clock error information. The receiving entity may further generate a position estimate based on the received location information.

BACKGROUND

Background Field

The subject matter disclosed herein relates to wireless communicationssystems, and more particularly to methods and apparatuses for locationdetermination of a user equipment in a wireless communications system.

RELEVANT BACKGROUND

Obtaining accurate position information for user equipment, such ascellular telephones or other wireless communication devices, is becomingprevalent in the communications industry. For example, obtaining highlyaccurate locations of vehicles or pedestrians is essential forautonomous vehicle driving and pedestrian safety applications.

A common means to determine the location of a device is to use asatellite positioning system (SPS), such as the well-known GlobalPositioning Satellite (GPS) system or Global Navigation Satellite System(GNSS), which employ a number of satellites that are in orbit around theEarth. In certain scenarios, however, location determination signalsfrom an SPS may be unreliable or unavailable, e.g., during adverseweather conditions or in areas with poor satellite signal reception suchas tunnels or parking complexes. Moreover, position informationgenerated using SPS is prone to imprecision. For example, off-the-shelfGPS positioning devices have an accuracy of a few meters, which is notoptimal to ensure safe autonomous driving and navigation.

Coordinated or automated driving requires communications betweenvehicles, which may be direct or indirect, e.g., via an infrastructurecomponent such as a roadside unit (RSU). For vehicle safetyapplications, both positioning and ranging are important. For example,vehicle user equipments (UEs) may perform positioning and ranging usingsidelink signaling, e.g., broadcasting ranging signals for other vehicleUEs or pedestrian UEs to determine the relative location of thetransmitter. An accurate and timely knowledge of the relative locationsor ranges to nearby vehicles, enables automated vehicles to safelymaneuver and negotiate traffic conditions. Round trip time (RTT), forexample, is a technique commonly used for determining a range betweentransmitters. RTT is a two-way messaging technique in which the timebetween sending a signal from a first device to receiving anacknowledgement from a second device (minus processing delays)corresponds to the distance (range) between the two devices. While RTTis accurate, it would be desirable to reduce the power consumptionrequired by two way messaging.

SUMMARY

A user equipment (UE) in a vehicle (V-UE) broadcasts multi-phasedranging signals on a sidelink channel with which other entities,including V-UE, UEs held by pedestrian and Road Side Units (RSUs) maydetermine the range to the V-UE. The multi-phased ranging signals is asequence of signals. A first message, which may be broadcast in theIntelligent Transport System (ITS) spectrum, includes ranginginformation, such as a source identifier, location information for thebroadcasting V-UE, and an expected time of broadcast of the rangingsignal. The ranging signal may then be broadcast at the expected timeand may include the source identifier. A second message, which bebroadcast in the ITS spectrum, may include clock error information forthe V-UE. A receiving entity may determine the range to the V-UE basedon the time of arrival of the ranging signal and the expected time oftransmission, as well as the clock error information. The receivingentity may further generate a position estimate based on the receivedlocation information.

In one implementation, a method of ranging between vehicles performed bya vehicle based user equipment (V-UE), includes broadcasting one or moremessages with information related to a ranging signal, the informationcomprising a source identifier identifying the V-UE, locationinformation for the V-UE, clock error information for the V-UE, and atime of broadcast of a ranging signal, the one or more messagesbroadcast before, or after, or both before and after broadcasting theranging signal; and broadcasting the ranging signal, the ranging signalcomprising the source identifier.

In one implementation, a vehicle based user equipment (V-UE) configuredfor ranging between vehicles, includes a wireless transceiver configuredto receive broadcast signals from other V-UEs; at least one memory; andat least one processor coupled to the wireless transceiver and the atleast one memory, the at least one processor configured to: broadcastone or more messages with information related to a ranging signal, theinformation comprising a source identifier identifying the V-UE,location information for the V-UE, clock error information for the V-UE,and a time of broadcast of a ranging signal, the one or more messagesbroadcast before, or after, or both before and after broadcasting theranging signal; and broadcast the ranging signal, the ranging signalcomprising the source identifier.

In one implementation, a vehicle based user equipment (V-UE) configuredfor ranging between vehicles, includes means for broadcasting a firstmessage with information related to a ranging signal, the informationcomprising a source identifier identifying the V-UE and locationinformation for the V-UE; means for broadcasting one or more messageswith information related to a ranging signal, the information comprisinga source identifier identifying the V-UE, location information for theV-UE, clock error information for the V-UE, and a time of broadcast of aranging signal, the one or more messages broadcast before, or after, orboth before and after broadcasting the ranging signal; and means forbroadcasting the ranging signal, the ranging signal comprising thesource identifier.

In one implementation, a non-transitory storage medium including programcode stored thereon, the program code is operable to configure at leastone processor in a vehicle based user equipment (V-UE) configured forranging between vehicles, includes program code to broadcast one or moremessages with information related to a ranging signal, the informationcomprising a source identifier identifying the V-UE, locationinformation for the V-UE, clock error information for the V-UE, and atime of broadcast of a ranging signal, the one or more messagesbroadcast before, or after, or both before and after broadcasting theranging signal; and program code to broadcast the ranging signal, theranging signal comprising the source identifier.

In one implementation, a method of ranging between vehicles performed bya first vehicle based user equipment (V-UE), includes receiving one ormore messages broadcast by a second V-UE, the one or more messagescomprising information related to a ranging signal to be broadcast bythe second V-UE, the information comprising a source identifieridentifying the second V-UE, location information for the second V-UE,clock error information for the second V-UE, and a time of broadcast ofa ranging signal, the one or more messages is received before, or after,or both before and after receiving the ranging signal; receiving theranging signal broadcast by the second V-UE, the ranging signalcomprising the source identifier; and determining a range to the secondV-UE based on the information related to the ranging signal, the rangingsignal, and the clock error information received from the second V-UE.

In one implementation, a first vehicle based user equipment (V-UE)configured for ranging between vehicles, includes a wireless transceiverconfigured to receive broadcast signals from other V-UEs; at least onememory; and at least one processor coupled to the wireless transceiverand the at least one memory, the at least one processor configured to:receive one or more messages broadcast by a second V-UE, the one or moremessages comprising information related to a ranging signal to bebroadcast by the second V-UE, the information comprising a sourceidentifier identifying the second V-UE, location information for thesecond V-UE, clock error information for the second V-UE, and a time ofbroadcast of a ranging signal, the one or more messages is receivedbefore, or after, or both before and after receiving the ranging signal;receive the ranging signal broadcast by the second V-UE, the rangingsignal comprising the source identifier; and determine a range to thesecond V-UE based on the information related to the ranging signal, theranging signal, and the clock error information received from the secondV-UE.

In one implementation, a first vehicle based user equipment (V-UE)configured for ranging between vehicles, includes means for receivingone or more messages broadcast by a second V-UE, the one or moremessages comprising information related to a ranging signal to bebroadcast by the second V-UE, the information comprising a sourceidentifier identifying the second V-UE, location information for thesecond V-UE, clock error information for the second V-UE, and a time ofbroadcast of a ranging signal, the one or more messages is receivedbefore, or after, or both before and after receiving the ranging signal;means for receiving the ranging signal broadcast by the second V-UE, theranging signal comprising the source identifier; and means fordetermining a range to the second V-UE based on the information relatedto the ranging signal, the ranging signal, and the clock errorinformation received from the second V-UE.

In one implementation, a non-transitory storage medium including programcode stored thereon, the program code is operable to configure at leastone processor in a first vehicle based user equipment (V-UE) configuredfor ranging between vehicles, includes program code to receive one ormore messages broadcast by a second V-UE, the one or more messagescomprising information related to a ranging signal to be broadcast bythe second V-UE, the information comprising a source identifieridentifying the second V-UE, location information for the second V-UE,clock error information for the second V-UE, and a time of broadcast ofa ranging signal, the one or more messages is received before, or after,or both before and after receiving the ranging signal; program code toreceive the ranging signal broadcast by the second V-UE, the rangingsignal comprising the source identifier; and program code to determine arange to the second V-UE based on the information related to the rangingsignal, the ranging signal, and the clock error information receivedfrom the second V-UE.

BRIEF DESCRIPTION OF THE DRAWING

Non-limiting and non-exhaustive aspects are described with reference tothe following figures, wherein like reference numerals refer to likeparts throughout the various figures unless otherwise specified.

FIG. 1 illustrates a wireless communication system illustratinginter-vehicle communications, including multi-phased ranging signalingto support single sided ranging and positioning.

FIG. 2 shows a structure of an example subframe sequence withpositioning reference signal (PRS) positioning occasions.

FIG. 3 illustrates an exemplary PRS configuration for a cell supportedby a wireless node.

FIG. 4 is a block diagram of a base station in communication with a UEin an access network.

FIG. 5 illustrates signaling flow for a multi-phased ranging procedure.

FIG. 6 illustrates an environment in which a V-UE determines its rangeand position based on ranging signals from multiple other V-UEs.

FIG. 7 illustrates an environment in which a V-UE determines its clockerror based on ranging signals from multiple other V-UEs.

FIG. 8 shows a schematic block diagram illustrating certain exemplaryfeatures of a V-UE configured for a multi-phased ranging procedure.

FIG. 9 is a flow chart illustrating a method of ranging between vehiclesperformed by a V-UE.

FIG. 10 is a flow chart illustrating another method of ranging betweenvehicles performed by a V-UE.

DETAILED DESCRIPTION

Inter-vehicle communications may be used, for example, for automateddriving and vehicle safety applications. Inter-vehicle communicationsmay be direct, e.g., vehicle to vehicle, or may be indirect, e.g., viaan infrastructure component such as a roadside unit (RSU). Theinter-vehicle communications may include messaged and informationelements (IEs) with which a vehicle may provide information necessaryfor automated driving

For example, for safe operation of autonomous vehicles, the relativelocations or ranges to other vehicles needs to be determined. Variousapproaches may be used to derive the relative positions betweenvehicles. For example, relative positions of vehicles may be derivedusing ranging signaling. Ranging signals are sometimes referred to asphysical ranging signals, positioning ranging signals, positioningreference signals, or physical referencing signals, and may becollectively referred to herein as PRS signals. PRS signals, forexample, may be broadcast by a user equipment (UE) in a vehicle,sometimes referred to as V-UE, and received by other V-UEs and/orinfrastructure using direct communication systems, such as dedicatedshort-range communication (DSRC), cellular Vehicle-to-Everything (C-V2X)communication, and even 5G New Radio (NR) communications. PRS signals,are used to determine a range to the broadcasting vehicle, e.g., usingone way ranging, round-trip-time (RTT) positioning operations, or otherstandard positioning operations such as time of arrival (TOA), timedifference of arrival (TDOA) or observed time difference of arrival(OTDOA).

In general, for single-sided ranging, vehicles (or pedestrians) maybroadcast PRS in sidelink signaling so that all other nearby vehicles(or pedestrians) may receive the broadcast PRS and determine the rangeto the broadcasting vehicle. If the broadcasting vehicles have knownpositions, the position of the receiving vehicle may be determined basedon the range to the broadcasting vehicles and their known positions.Thus, ranging and positioning of distributed devices (vehicles orpedestrians) may be enabled using PRS signals over sidelink withoutinfrastructure support.

In some implementations, multi-phased ranging signals may be broadcastby a V-UE on a sidelink channel. The multi-phased ranging signals, forexample, is a sequence of broadcast signals, which may include a firstmessage that includes ranging information for the ranging signal to bebroadcast. The ranging information, for example, may include a sourceidentifier, location information for the broadcasting V-UE, and anexpected time of broadcast of the ranging signal. The ranging signal maythen be broadcast at the expected time and may include the sourceidentifier. A second message may be broadcast that include clock errorinformation for the V-UE. A receiving entity may determine the range tothe V-UE based on the time of arrival of the ranging signal and theexpected time of transmission, as well as the clock error information.The receiving entity may further generate a position estimate based onthe received location information and ranges and location informationfor additional V-UEs.

FIG. 1 illustrates a wireless communication system 100 illustratinginter-vehicle communications, including multi-phased ranging signalingto support single sided ranging and positioning, as described herein.Wireless communication system 100 illustrates a first vehicle 102 with afirst wireless device, e.g., V-UE 102, in wireless communications withanother V-UE 104, illustrated as a second vehicle. The V-UE 102 andV-UE104 may comprise, but are not limited to, an on board unit (OBU), avehicle or subsystem thereof, or various other communication devices.The V-UEs 102 and 104 function and provide communications on behalf oftheir associated vehicles and, accordingly, may be sometimes referred toherein simply as vehicles 102 and 104. The first vehicle 102 and secondvehicle 104, for example, may be two vehicles traveling on a road alongwith other vehicles, not illustrated.

The wireless communication system 100 may use, e.g.,Vehicle-to-Everything (V2X) communication standard, in which informationis passed between a vehicle and other entities within the wirelesscommunication network. The V2X services include, e.g., services forVehicle-to-Vehicle (V2V), Vehicle-to-Pedestrian (V2P),Vehicle-to-Infrastructure (V2I), and Vehicle-to-Network (V2N). The V2Xstandard aims to develop autonomous or semi-autonomous driving systems,such as ADAS, which helps drivers with critical decisions, such as lanechanges, speed changes, overtaking speeds, and may be used to assist inparking as discussed herein. Low latency communications are used in V2Xand, are therefore suitable for precise relative positioning, e.g.,using ranging signals, such as one way ranging, RTT, TDOA, etc.

In general, there are two modes of operation for V2X services, asdefined in Third Generation Partnership Project (3GPP) TS 23.285. Onemode of operation uses direct wireless communications between V2Xentities when the V2X entities. The other mode of operation uses networkbased wireless communication between entities. The two modes ofoperation may be combined, or other modes of operation may be used ifdesired.

As illustrated in FIG. 1, the wireless communication system 100 mayoperate using direct or indirect wireless communications between thevehicle 102 and vehicle 104. For example, the wireless communication maybe over, e.g., Proximity-based Services (ProSe) Direction Communication(PC5) reference point as defined in 3GPP TS 23.303, and may use wirelesscommunications under IEEE 1609, Wireless Access in VehicularEnvironments (WAVE), Intelligent Transport Systems (ITS), and IEEE802.11p, on the ITS band of 5.9 GHz, or other wireless connectionsdirectly between entities. Thus, as illustrated, vehicle 102 and vehicle104 may directly communicate using with a Vehicle-to-Vehicle (V2V)communication link 105.

In other implementations, vehicle 102 and vehicle 104 may indirectlycommunicate, e.g., through a roadside unit (RSU) 110 viaVehicle-to-Infrastructure (V2I) communication links 112 and 114,respectively. The RSU 110, for example, may be a stationaryinfrastructure entity, that may support V2X applications and that canexchange messages with other entities supporting V2X applications. AnRSU may be a logical entity that may combine V2X application logic withthe functionality of base stations in a RAN, such as an eNB, ng-eNB, oreLTE (referred to as eNB-type RSU) or a gNB, or UE (referred to asUE-type RSU). The vehicles 102, 104 and RSU 110 may communicate withadditional entities, such as additional vehicles, RSUs or pedestrians(not shown) using direct or indirect communication links. The RSU 110may be capable of determining relative ranges of vehicles 102 and 104using PRS broadcast by the vehicles 102 and 104.

During direct communications with one or more entities in the V2Xwireless communication system 100, each entity may provide V2Xinformation, such as an identifier for the V2X entity, as well as otherinformation in messages such as Common Awareness Messages (CAM) andDecentralized Notification Messages (DENM) or Basic Safety Message(BSM), which may be used for, e.g., Advanced Driver Assistance System(ADAS) or safety use cases.

Additionally, as illustrated in FIG. 1, the wireless communicationsystem 100 may operate using indirect wireless communications, e.g.,using cellular vehicle-to-everything (CV2X). For example, vehicles maycommunicate via a base station 122 in a Radio Access Network (RAN), suchas an evolved Node B (eNB) or next generation evolved Node B (ng-eNB) inLTE wireless access and/or evolved LTE (eLTE) wireless access or a NRNode B (gNB) in Fifth Generation (5G) wireless access. Thus, asillustrated, the vehicles 102 and 104 may wirelessly communicate with abase station 122 in the network infrastructure 120, via communicationlinks 123 and 125. In some implementations, the base station 122 maydirectly communicate with the RSU 110 via communication link 116. Thebase station 122 may also communicate with other base stations 124through the IP layer 126 and network 128, such as an Evolved MultimediaBroadcast Multicast Services (eMBMS)/Single Cell Point To Multipoint(SC-PTM) network. A V2X application server 130 may be part of orconnected to the IP layer 126 and may receive and route informationbetween the V2X entities as well as receive other external inputs. Thebase station 124 may wirelessly communicate with the other V2X entities,such as the RSU 110 via communication link 127 or vehicles 102 and 104via communication links (not shown).

Vehicles 102 and 104 may broadcast PRS on links 105, 112, 114, 123 or125, with which the range or relative positions between vehicles 102 and104 may be determined. The PRS broadcast by vehicles 102 and 104 may beany signal suitable for ranging, e.g., as defined for DSRC or C-V2X. ThePRS may be broadcast on licensed or unlicensed spectrum. For example, insome implementations, PRS may be broadcast on one or more UnlicensedNational Information Infrastructure (UNII) radio bands including, forexample, one or more of the UNII-1 radio band, the UNII-2A radio band,the UNII-2B radio band, or the UNII-3 radio band. When broadcast onunlicensed spectrum, listen before transmit (LBT) protocols may beemployed.

For example, where vehicles 102 and 104 broadcast PRS in a V2V link 105,the range or relative positions between vehicles 102 and 104 may bedetermined directly, e.g., using one way ranging. On the other hand,where vehicles 102 and 104 broadcast PRS in V2I links 112 and 114 or vialinks 123 and 125, the range or relative positions between vehicles 102and 104 may be determined indirectly based on the range or relativepositions between vehicle 102 and RSU 110 (or base station 122) and therange or relative positions between vehicle 104 and RSU 110 (or basestation 122), which may be determined using one way ranging.

The V2V communications based on direct wireless communications betweenthe vehicles 102 and 104, do not require any network infrastructure andenable low latency communications, which is advantageous for preciseranging or positioning. Accordingly, such direct wireless V2Vcommunications may be desirable for ranging over short distances, e.g.,with nearby vehicles, whereas ranging with vehicles over extendeddistances have more relaxed latency requirements, and therefore may beable to utilize the vehicle to vehicle signaling via V2V link 105 aswell as the vehicle to infrastructure signaling via links 112 and 114 orvia links 123 and 125.

FIG. 2 shows a structure of an example subframe sequence 200 with PRSpositioning occasions. Subframe sequence 200 may be applicable tobroadcast PRS signals from V-UEs 102 and 104 in wireless communicationsystems 100. While FIG. 2 provides an example of a subframe sequence forLong Term Evolution (LTE) under The 3rd Generation Partnership Project(3GPP), similar subframe sequence implementations may be realized forother communication technologies/protocols, including V2X.

In FIG. 2, time is represented horizontally (e.g., on an X axis) withtime increasing from left to right, while frequency is representedvertically (e.g., on a Y axis) with frequency increasing (or decreasing)from bottom to top. As shown in FIG. 2, downlink and uplink Radio Frames210 may be of 10 ms duration each. For downlink Frequency DivisionDuplex (FDD) mode, Radio Frames 210 are organized, in the illustratedembodiments, into ten subframes 212 of 1 ms duration each. Each subframe212 comprises two slots 214, each of, for example, 0.5 ms duration.

In the frequency domain, the available bandwidth may be divided intouniformly spaced orthogonal subcarriers 216. For example, for a normallength cyclic prefix using, for example, 15 kHz spacing, subcarriers 216may be grouped into a group of twelve (12) subcarriers. Each grouping,which comprises the 12 subcarriers 216, is termed a resource block and,in the example above, the number of subcarriers in the resource blockmay be written as N_(SC) ^(RB)=12. For a given channel bandwidth, thenumber of available resource blocks on each channel 222, which is alsocalled the transmission bandwidth configuration 222, is indicated asN_(RB) ^(DL). For example, for a 3 MHz channel bandwidth in the aboveexample, the number of available resource blocks on each channel 222 isgiven by N_(RB) ^(DL)=15.

In the wireless communication system 100 illustrated in FIG. 1, a V-UE102 in sidelink communication with another V-UE 104, may transmitframes, or other physical layer signaling sequences, supporting PRSsignals (i.e. a sidelink PRS) according to frame configurations eithersimilar to, or the same as that, shown in FIG. 2 and (as describedlater) in FIG. 3, which may be measured and used for vehicle ranging. Asnoted, other types of wireless nodes (e.g., RSU 110) and base stations122, 124, may also be configured to transmit or receive PRS signalsconfigured in a manner similar to (or the same as) that depicted inFIGS. 2 and 3. Since transmission of a PRS by a wireless node or basestation is directed to all V-UEs within radio range, a wireless node orbase station can also be considered to transmit (or broadcast) a PRS.

A PRS, which has been defined in Third Generation Partnership Project(3GPP) LTE Release-9 and later releases, may be transmitted by wirelessnodes (e.g., base stations) after appropriate configuration (e.g., by anOperations and Maintenance (O&M) server). A PRS may be transmitted inspecial positioning subframes that are grouped into positioningoccasions. PRS occasions may be grouped into one or more PRS occasiongroups. For example, in LTE, a PRS positioning occasion can comprise anumber N_(PRS) of consecutive positioning subframes where the numberN_(PRS) may be between 1 and 160 (e.g., may include the values 1, 2, 4and 6 as well as other values). The PRS positioning occasions for a cellsupported by a wireless node may occur periodically at intervals,denoted by a number T_(PRS), of millisecond (or subframe) intervalswhere T_(PRS) may equal 5, 10, 20, 40, 80, 160, 320, 640, or 1280 (orany other appropriate value). As an example, FIG. 2 illustrates aperiodicity of positioning occasions where N_(PRS) equals 4218 andT_(PRS) is greater than or equal to 20220. In some aspects, T_(PRS) maybe measured in terms of the number of subframes between the start ofconsecutive positioning occasions.

FIG. 3 illustrates an exemplary PRS configuration 300 for a cellsupported by a wireless node (such as a base station). Again, PRStransmission for LTE is assumed in FIG. 3, although the same or similaraspects of PRS transmission to those shown in and described for FIG. 3may apply to sidelink transmission between V-UEs 102, 104 in V2X, and/orother wireless technologies. FIG. 3 shows how PRS positioning occasionsare determined by a System Frame Number (SFN), a cell specific subframeoffset (Δ_(PRS)) 352, and the PRS Periodicity (T_(PRS)) 320. Typically,the cell specific PRS subframe configuration is defined by a “PRSConfiguration Index”/PRS included in the OTDOA assistance data. The PRSPeriodicity (T_(PRS)) 320 and the cell specific subframe offset(Δ_(PRS)) are defined based on the PRS Configuration Index I_(PRS), in3GPP TS 36.211 entitled “Physical channels and modulation.” A PRSconfiguration is defined with reference to the System Frame Number (SFN)of a cell that transmits PRS. PRS instances, for the first subframe ofthe N_(PRS) downlink subframes comprising a first PRS positioningoccasion, may satisfy:

(10×n _(f) +└n _(s)/2┘−Δ_(PRS))mod T _(PRS)=0,

where n_(f) is the SFN with 0≤n_(f)≤1023, n_(s) is the slot numberwithin the radio frame defined by n_(f) with 0≤n_(s)≤19, T_(PRS) is thePRS periodicity 320, and APRs is the cell-specific subframe offset 352.

As shown in FIG. 3, the cell specific subframe offset Δ_(PRS) 352 may bedefined in terms of the number of subframes transmitted starting fromSystem Frame Number 0 (Slot ‘Number 0’, marked as slot 350) to the startof the first (subsequent) PRS positioning occasion. In the example inFIG. 3, the number of consecutive positioning subframes (N_(PRS)) ineach of the consecutive PRS positioning occasions 318 a, 318 b, and 318c equals 4.

Typically, PRS occasions from all cells in a network that use the samefrequency are aligned in time and may have a fixed known time offset(e.g., cell-specific subframe offset 352) relative to other cells in thenetwork that use a different frequency. In SFN-synchronous networks allwireless nodes (e.g., base stations) may be aligned on both frameboundary and system frame number. Therefore, in SFN-synchronous networksall cells supported by the various wireless nodes may use the same PRSconfiguration index for any particular frequency of PRS transmission. Onthe other hand, in SFN-asynchronous networks, the various wireless nodesmay be aligned on a frame boundary, but not system frame number. Thus,in SFN-asynchronous networks the PRS configuration index for each cellmay be configured separately by the network so that PRS occasions alignin time.

As defined by 3GPP (e.g., in 3GPP TS 36.211), for LTE systems, thesequence of subframes used to transmit PRS (e.g., for OTDOA positioning)may be characterized and defined by a number of parameters, as describedpreviously, comprising: (i) a reserved block of bandwidth (BW), (ii) theconfiguration index I_(PRS), (iii) the duration N_(PRS), (iv) anoptional muting pattern; and (v) a muting sequence periodicity T_(RE)pthat can be implicitly included as part of the muting pattern in (iv)when present. In some cases, with a fairly low PRS duty cycle,N_(PRS)=1, T_(PRS)=160 subframes (equivalent to 160 ms), and BW=1.4, 3,5, 10, 15, or 20 MHz. To increase the PRS duty cycle, the N_(PRS) valuecan be increased to six (i.e., N_(PRS)=6) and the bandwidth (BW) valuecan be increased to the system bandwidth (i.e., BW=LTE system bandwidthin the case of LTE). An expanded PRS with a larger N_(PRS) (e.g.,greater than six) and/or a shorter T_(PRS) (e.g., less than 160 ms), upto the full duty cycle (i.e., N_(PRS)=T_(PRS)), may also be used inlater versions of LPP according to 3GPP TS 36.355. A directional PRS maybe configured as just described according to 3GPP TSs and may, forexample, use a low PRS duty cycle (e.g., N_(PRS)=1, T_(PRS)=160subframes) or a high duty cycle.

As noted above, the subframe sequence 200 with PRS positioning occasionsand PRS configuration 300 shown in FIGS. 2 and 3 are specific for LTE.Nevertheless, similar subframe sequence and PRS configurations may beused for V2X, e.g., with appropriate changes. For example, in someimplementations, for V2X, PRS candidate slots may be every 100 msec andmay spans 100 RB over a 20 MHz bandwidth.

The relative locations between vehicles may be determined as a rangebetween vehicles based on PRS. For example, a V-UE 102 may broadcastPRS, and may further transmit the time of transmission of the PRS, e.g.,in an ITS message, as described herein. The receiving V-UE 104 receivesthe PRS and uses the time of reception, as measured at V-UE 104 alongwith the time of transmission as provided by the V-UE 102 to determinethe time of flight of the PRS. The V-UE 104 may determine the distanceor range between the vehicles based on the time of flight and the speedof light.

FIG. 4 is a block diagram of a base station 410 in communication with aUE 450 in an access network. The UE 450, for example, may be a wirelessdevice such as V-UE 102, illustrated in FIG. 1. The base station 410,for example, may be the RSU 110, or one of base stations 122, 124, ormay be another wireless device, such as V-UE 104, illustrated in FIG. 1,using sidelink communications. In the DL from base station 410, IPpackets may be provided to a controller/processor 475. Thecontroller/processor 475 implements layer 4 and layer 2 functionality.Layer 4 includes a radio resource control (RRC) layer, and layer 2includes a service data adaptation protocol (SDAP) layer, a packet dataconvergence protocol (PDCP) layer, a radio link control (RLC) layer, anda medium access control (MAC) layer. The controller/processor 475provides RRC layer functionality associated with broadcasting of systeminformation (such as master information block (MIB), and systeminformation block (SIBs)), RRC connection control (such as RRCconnection paging, RRC connection establishment, RRC connectionmodification, and RRC connection release), inter radio access technology(RAT) mobility, and measurement configuration for UE measurementreporting; PDCP layer functionality associated with header compressionand decompression, security (such as ciphering, deciphering, integrityprotection, integrity verification), and handover support functions; RLClayer functionality associated with the transfer of upper layer packetdata units (PDUs), error correction through Automatic Repeat Request(ARQ), concatenation, segmentation, and reassembly of RLC service dataunits (SDUs), re-segmentation of RLC data PDUs, and reordering of RLCdata PDUs; and MAC layer functionality associated with mapping betweenlogical channels and transport channels, multiplexing of MAC SDUs ontotransport blocks (TBs), demultiplexing of MAC SDUs from TBs, schedulinginformation reporting, error correction through Hybrid Automatic RepeatRequest (HARQ), priority handling, and logical channel prioritization.

The transmit (TX) processor 416 and the receive (RX) processor 470implement layer 1 functionality associated with various signalprocessing functions. Layer 1, which includes a physical (PHY) layer,may include error detection on the transport channels, forward errorcorrection (FEC) coding/decoding of the transport channels,interleaving, rate matching, mapping onto physical channels,modulation/demodulation of physical channels, andmultiple-input/multiple-output (MIMO) antenna processing. The TXprocessor 416 handles mapping to signal constellations based on variousmodulation schemes (such as binary phase-shift keying (BPSK), quadraturephase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadratureamplitude modulation (M-QAM)). The coded and modulated symbols may thenbe split into parallel streams. Each stream may then be mapped to anorthogonal frequency-division multiplexing (OFDM) subcarrier,multiplexed with a reference signal (such as a pilot signal) in the timeor frequency domain, and then combined together using an Inverse FastFourier Transform (IFFT) to produce a physical channel carrying a timedomain OFDM symbol stream. The OFDM stream is spatially precoded toproduce multiple spatial streams. Channel estimates from a channelestimator 474 may be used to determine the coding and modulation scheme,as well as for spatial processing. The channel estimate may be derivedfrom a reference signal or channel condition feedback transmitted by theUE 450. Each spatial stream may then be provided to a different antenna420 via a separate transmitter 418TX. Each transmitter 418TX maymodulate an RF carrier with a respective spatial stream fortransmission.

At the UE 450, each receiver 454RX receives a signal through itsrespective antenna 452. Each receiver 454RX recovers informationmodulated onto an RF carrier and provides the information to the receive(RX) processor 456. The TX processor 468 and the RX processor 456implement layer 1 functionality associated with various signalprocessing functions. The RX processor 456 may perform spatialprocessing on the information to recover any spatial streams destinedfor the UE 450. If multiple spatial streams are destined for the UE 450,they may be combined by the RX processor 456 into a single OFDM symbolstream. The RX processor 456 converts the OFDM symbol stream from thetime-domain to the frequency domain using a Fast Fourier Transform(FFT). The frequency domain signal includes a separate OFDM symbolstream for each subcarrier of the OFDM signal. The symbols on eachsubcarrier, and the reference signal, are recovered and demodulated bydetermining the most likely signal constellation points transmitted bythe base station 410. These soft decisions may be based on channelestimates computed by the channel estimator 458. The soft decisions arethen decoded and deinterleaved to recover the data and control signalsthat were originally transmitted by the base station 410 on the physicalchannel. The data and control signals are then provided to thecontroller/processor 459, which implements layer 4 and layer 2functionality.

The controller/processor 459 can be associated with a memory 460 thatstores program codes and data. The memory 460 may be referred to as acomputer-readable medium. In the UL, the controller/processor 459provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, and control signalprocessing to recover IP packets. The controller/processor 459 is alsoresponsible for error detection using an acknowledgement (ACK) ornegative acknowledgement (NACK) protocol to support HARQ operations.

Similar to the functionality described in connection with the DLtransmission by the base station 410, the controller/processor 459provides RRC layer functionality associated with system informationacquisition, RRC connections, and measurement reporting; PDCP layerfunctionality associated with header compression and decompression, andsecurity (such as ciphering, deciphering, integrity protection, andintegrity verification); RLC layer functionality associated with thetransfer of upper layer PDUs, error correction through ARQ,concatenation, segmentation, and reassembly of RLC SDUs, re-segmentationof RLC data PDUs, and reordering of RLC data PDUs; and MAC layerfunctionality associated with mapping between logical channels andtransport channels, multiplexing of MAC SDUs onto TBs, demultiplexing ofMAC SDUs from TBs, scheduling information reporting, error correctionthrough HARQ, priority handling, and logical channel prioritization.

Channel estimates derived by a channel estimator 458 from a referencesignal or feedback transmitted by the base station 410 may be used bythe TX processor 468 to select the appropriate coding and modulationschemes, and to facilitate spatial processing. The spatial streamsgenerated by the TX processor 468 may be provided to different antenna452 via separate transmitters 454TX. Each transmitter 454TX may modulatean RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the base station 410 in a mannersimilar to that described in connection with the receiver function atthe UE 450. Each receiver 418RX receives a signal through its respectiveantenna 420. Each receiver 418RX recovers information modulated onto anRF carrier and provides the information to a RX processor 470.

The controller/processor 475 can be associated with a memory 476 thatstores program codes and data. The memory 476 may be referred to as acomputer-readable medium. In the UL, the controller/processor 475provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover IP packets from the UE 450. IP packets from thecontroller/processor 475 may be provided to a server, such as V2Xapplication server 130. The controller/processor 475 is also responsiblefor error detection using an ACK-NACK protocol to support HARQoperations.

Timing information, real-time traffic information, collision avoidanceinformation, and some other features provided by V2X communications andV2X channels of a RAN may depend, at least in part, on the ability of aV-UE to accurately determine its position relative to other vehicles orobstacles and to accurately determine distances between the V-UE andnearby vehicles or obstacles, i.e., ranging. In accordance with someaspects of the present disclosure, ranging signals (e.g., PRS signals)may be transmitted to nearby entities, e.g., other V-UEs, RSUs,pedestrians, etc. The PRS may be transmitted single-sided, i.e., withoutuse of acknowledgement messages. The receiving V-UE may measure the timeof arrival (TOA) of a single-sided ranging signal, but the transmissiontime of the ranging signals will be unknown. Accordingly, in addition tobroadcasting the ranging (PRS) signals, the V-UE needs to broadcastadditional information with which the receiving V-UE may use todetermine the determine the range to the broadcasting V-UE. Thetransmitting V-UE may broadcast additional information as well withwhich the receiving V-UE, for example, may increase accuracy of theranging measurement or determine position.

In one implementation, ranging may be performed using multi-phasedsignaling by a transmitting V-UE via sidelink signaling. For example,one or more phases, message(s) may be broadcast that include informationabout the ranging signal, and in another phase, the ranging signal maybe broadcast. For example, in a first phase, the transmitting V-UE maybroadcast a message that includes information related to an upcomingranging signal. For example, the first message may be broadcast in theITS spectrum. The second phase may be the broadcast of the a physicalranging signal, such as a PRS signal. The third phase may be thebroadcast of another message that includes information related to thepreviously transmitted ranging signal. For example, this second messagemay be broadcast in the ITS spectrum. Information may be transmittedinterchangeably between the first and third phase or the first and thirdphase may be combined. The multi-phase signaling is a single rangingprocedure, with which a receiving V-UE may determine the range to thetransmitting V-UE. The single ranging procedure may be repeated multipletimes.

In the first stage, for example, a transmitting V-UE 102 may prepare afirst message that includes information related to an ranging signal andsends the first message, via broadcast. The first message, for example,may include ranging information, such as a device-specific sourceidentifier (ID), e.g., identifying the V-UE 102, location informationfor the V-UE 102, and the time of the broadcast of the ranging signalmay be included, e.g., if the ranging signal is broadcast on a licensedspectrum. The expected time of broadcast, for example, may be based on auniversal time acquired via the IP layer 126 and network 128. In someimplementations, the location information of the V-UE 102 may include acurrent location of the V-UE 102 and the velocity of the V-UE 102 (e.g.,the absolute speed and direction). In some implementations, the locationinformation may include the expected location of the V-UE 102 at theexpected time of broadcast of the ranging signal, which may bedetermined based on the current location and velocity and the time untilthe broadcast of the ranging signal. The first message may betransmitted, e.g., in the ITS spectrum, to nearby receivers such as V-UE104 or UEs used by pedestrians, or RSU 110, via broadcast.

In the second stage, the transmitting V-UE 102 broadcasts the rangingsignal, e.g., the PRS signal, at the expected time, as indicated in thefirst message. The ranging signal may contain the device-specific sourceID that was provided in the first message so that the receiving devicemay associate the broadcast ranging signal with the previously broadcastfirst message. The ranging signal may also contains sequence ID thatidentifies the ranging signal with respect to other ranging signalsbroadcast by V-UE 102 or with respect to other ranging signals broadcastby other transmitters. In some implementations, the source ID and thesequence ID may be the same ID. In one embodiment, the PRS waveform maybe based on one or more of the source ID and the sequence ID, or acombination thereof, so that V-UE 104 that receives the PRS waveform maydeduce the PRS source and sequence from the signaling itself. Forexample, the PRS waveforms may be included in a set, and depending onthe source ID (and/or sequence ID), the transmitting V-UE 102 may selectone of the PRS waveforms from the set. The selected PRS waveform maythus, provide an indication of the source ID and sequence ID for theV-UE 102.

In the third stage, the transmitting V-UE 102 prepares a second messagethat includes information related to the previously broadcast rangingsignal and sends the second message, via broadcast. The second message,for example, may include information such as the clock error informationof the transmitting V-UE 102, as well as the source ID and the time theranging signal was broadcast, e.g., if the ranging signal was broadcaston an unlicensed spectrum. In some implementations, the V-UE 102 mayindirectly determine the clock error between broadcasting the firstmessage and broadcasting the ranging signal, e.g., using receivedranging signals from other nearby transmitters. The second message mayalso include the variance of the clock error of the V-UE 102, which mayalso be determined indirectly using received ranging signals from othernearby transmitters. In some implementations, the third phase may beskipped, for example, if the clock error is unavailable to the V-UE 102or such procedure is unnecessary for the receiving V-UE 104. In otherimplementations, the first phase may be combined with the third phase,e.g., and may be sent either before or after broadcast of the rangingsignals.

The receiving device may determine the range to the transmitting devicebased on the difference between the time of arrival of the rangingsignal at the receiving device and the time of broadcast from thetransmitting device, e.g., as provided in the first message. Thedifference between the time of arrival and the time of transmission isthe time of flight of the ranging signal. The time of flight may bedivided by the speed of the ranging signal, i.e., the speed of light, todetermine the distance between the receiving device and the transmittingdevice. Because the transmitting device and receiving device are notsynchronized, however, a clock error may affect the accuracy of themeasurement. Clock error, for example, is intrinsic to each device. Theclock error, for example, may be due to clock drift and clock bias, andmay generally be written as:

clock_error=bias+drift*time.  Eq. 1

The clock bias, may be due to various aspects of the system, such asTx/Rx calibration error, oscillator bias, synchronization error, etc.The clock drift is due to the divergence of the clocks at the differentV-UEs. A clock error may be determined by each device, but the clockerror in a single V-UE is not useful since the total ranging errorcontributed by clock error is from two sources, i.e., the clock error inthe time of departure (TOD) from the V-UE 102 and the clock error in thetime of arrival (TOA) at the V-UE 104. By way of example, the measuredrange between the transmitting V-UE 102 and the receiving V-UE 104 asmeasured at the receiving V-UE 104 will include a clock error, and maybe written as:

$\begin{matrix}{{Range} = {{\frac{1}{c}{{{TOD} - {TOA}}}} + {{clock}_{-}{{error}.}}}} & {{Eq}.\mspace{14mu} 2}\end{matrix}$

The measured range differs from the true range by the clock error. Theclock error includes components from both the transmitting V-UE 102measured and the receiving device V-UE 104, i.e., both devices includeclock errors due to clock bias and drift. Accordingly, for a moreaccurate range measurement, the clock error may be determined by thetransmitting device V-UE 102 and transmitted to the receiving deviceV-UE 104. The clock error information from the transmitting device V-UE102 may be used by the receiving device V-UE 104 (e.g., along with clockerror information for the receiving device V-UE 104) to improve theaccuracy of the range measurement, e.g., by removing the clock errorcomponent due to the transmitting device V-UE 102, the receiving deviceV-UE 104, or both. For example, the receiving device V-UE 104 may adjustthe time of departure TOD as received from the transmitting V-UE 104based on the clock error information received from the transmittingdevice V-UE 104. The receiving device V-UE 104 may further adjust thetime of arrival (TOA) as measured at the receiving device V-UE 104 basedon the determined clock error for the receiving device V-UE 104.

The multi-phase signaling procedure may be repeated multiple times. Foreach multi-phase signaling, at each different time instance, a newmessage is broadcast for each phase, e.g., a new first message with thesource ID, the location information for the V-UE 102, the velocity ofthe V-UE 102, and the expected time of broadcast of the ranging signal,a new ranging signal, with the source ID and optionally a sequence ID,and a new second message with the current clock error information. Thesequence ID may be generated at the group phase. For example, the UEsare grouped together every 1000 msec. In this group phase, the sequenceID may be defined and used within that period. To accurately derive thelocation of a receiving V-UE 104, the V-UE 104 may receive multi-phasedsignaling from multiple transmitters and may determine the range to eachtransmitter, which along with the positions of each transmitter (e.g.,provided in the first message from each transmitter), may be used todetermine the position of the receiving V-UE 104, e.g. usingtrilateration. In some implementations, knowledge of the location of theroad and local geography, which may be obtained through the IP layer 126and network 128, shown in FIG. 1, may be used to assist in positioningof the V-UE 104.

The use of multi-phased ranging signaling, thus, provides a way toderive the range and location of vehicles or pedestrians without relyingon existing infrastructure. The various messages sent before and/orafter the broadcast of the ranging signal provides the information withwhich nearby receivers may derive their range to the transmitter andtheir locations using sidelink communications, which may be broadcast inunlicensed or licensed spectrums, and does not require acknowledgementor return messages, thereby reducing overhead.

FIG. 5 illustrates an example of a signaling flow 500 for a multi-phasedranging procedure that includes multiple entities, including V-UE1 502,V-UE2 504, V-UE3 506, and V-UE4 508. The V-UE entities, for example, maybe similar to V-UE 102, 104 shown in FIG. 1 or entities 410 and 450 inFIG. 4. In some implementations, one or more of the V-UEs may be apedestrian UE or a RSU, such as RSU 110, shown in FIG. 1. It should beunderstood that FIG. 5 illustrates the signaling for the multi-phasedranging procedure, and that additional or other communications may betransmitted between one or more of the V-UEs shown in FIG. 5 in sidelinksignaling or through one or more infrastructure devices, such as RSU 110or base stations 122, 124 shown in FIG. 1. Additionally, FIG. 5illustrates the multi-phased signaling from each V-UE at separatedistinct times, e.g., stages 1A-1C from V-UE1 502 and stage 5 fromV-UE3. It should be understood, however, that the multi-phased signalingfrom the various V-UEs may interleave.

As illustrated, in a first sequence, including stages 1A, 1B, and 1C,the V-UE1 502 broadcasts multi-phase signaling for ranging. At stage 1A,the transmitting V-UE1 502 broadcasts a first message that includes oneor more of ranging information, a source ID identifying the V-UE1 502,location information for the V-UE1 502, and the expected time of thebroadcast of the ranging signal, e.g., if the PRS broadcast is on alicensed spectrum, or a combination thereof. The location informationmay include, for example, a current location and velocity of the V-UE1502 (e.g., determined from a magnetometer, and wheel sensor or othersensor capable of determining velocity) or the expected location of theV-UE1 502 at the expected time of broadcast of the ranging signal, whichmay be determined based on the current location and velocity of theV-UE1 501 and the amount of time until the broadcast of the rangingsignal (if the PRS broadcast is on a licensed spectrum. The firstmessage may be a broadcast on an unlicensed or licensed spectrum, suchas the ITS spectrum. The broadcast first message may be received by anynearby entity, such as V-UE2 504, V-UE3 506, and V-UE4 508.

At stage 1B, the transmitting V-UE1 502 broadcasts the ranging signal,which may be a PRS signal. The ranging signal may include the source IDand may further include a sequence ID, e.g., identifying the sequence ofmulti-phase signaling from the V-UE1 502 (the source ID and sequence IDmay be the same). For example, the PRS waveforms may be selected from aset of pre-defined PRS waveforms that are each associated with an ID.The V-UE1 502 may select the PRS waveform based on its source ID and/orsequence ID (e.g., provided in the message at stage 1A). Upon receipt ofthe broadcast ranging signal, the receiving V-UE's may deduce the sourceID and sequence ID for the V-UE1 502 based on the PRS waveform andassociated ID as provided in the set of pre-defined PRS waveforms. Theranging signal may be a broadcast on an unlicensed or licensed spectrum.The broadcast ranging signal may be received by any nearby entity, suchas V-UE2 504, V-UE3 506, and V-UE4 508, which determines the time ofarrival of the ranging signal.

At stage 1C, the transmitting V-UE1 502 broadcasts additional ranginginformation in a second message, including one or more of clock errorinformation, the time of the broadcast of the ranging signal (at stage1B), e.g., if the PRS broadcast was on an unlicensed spectrum, or acombination thereof. The time of the broadcast of the ranging signal asprovided in stage 1C is provided if the PRS broadcast is on anunlicensed spectrum, while the expected time of broadcast of the rangingsignal as provided in stage 1A is provided if the PRS broadcast is on alicensed spectrum. The clock error information of the transmitting V-UE1502, for example, may be one or more of clock drift, clock bias, thevariance in clock drift, and variance in the clock bias, or acombination thereof. The clock error information is obtained by V-UE1502 indirectly by the multi-phased ranging procedure from nearbyentities, e.g., V-UE3 506 at stage 5 and V-UE4 508 at stage 7. Thesecond message may further include the source ID and sequence ID. Thesecond message may be a broadcast on an unlicensed or licensed spectrum,such as the ITS spectrum. The broadcast second message may be receivedby any nearby entity, such as V-UE2 504, V-UE3 506, and V-UE4 508. Insome implementations, the first message and the second message may becombined into a single message that may be broadcast, e.g., at stage 1Aor at stage 1C.

At stage 2, a V-UE2 504 may use the broadcast first sequence ofsignaling received at stages 1A, 1B, and 1C, to determine the rangebetween the V-UE2 504 and the transmitting V-UE1 502. The receivingV-UE2 504 may associate the first and second messages and the rangingsignal received at stages 1A, 1B, and 1C, e.g., based on the source IDand/or sequence ID included in each message and, e.g. embedded in thePRS waveform. For example, V-UE2 504 may determine the source ID andsequence ID for the V-UE1 502 based on the ID associated with the PRSwaveform as provided in the set of pre-defined PRS waveforms. The rangebetween the V-UE2 504 and the transmitting V-UE1 502 may be determined,for example, using the expected time of broadcast of the licensedranging signal from the first message received at stage 1A or the timeof broadcast of the unlicensed ranging signal received at stage 1Cprovides and the time of arrival of the ranging signal as measured byV-UE2 504. The difference between the time of broadcast and time ofarrival is the travel time for the ranging signal. The range (distance)between the receiving V-UE2 504 and the transmitting V-UE1 502 is thetime of travel of the ranging signal divided by the speed of the rangingsignal, i.e., the speed of light. The receiving V-UE2 504 may adjust thedetermined range, e.g. by adjusting the time of broadcast (or the timeof arrival), based on the clock error information received at stage 1C,to improve the accuracy of the determined range information. Thereceiving V-UE2 504 may additionally or alternatively adjust thedetermined range, e.g. by adjusting the time of arrival (or the time ofbroadcast) based on the receiving V-UE2 504 own clock error asdetermined by the receiving V-UE2 504 to improve the accuracy of thedetermined range information.

The receiving V-UE2 504 may further determine a position estimate basedon the determined range to the transmitting V-UE1 502 and the positionof the transmitting V-UE1 502 at the time of broadcast of the rangingsignal. A position estimate, for example, may be at least partiallybased on knowledge of the location of the road and local geography, forexample, eliminating positions that are not probably or possible for thereceiving V-UE2 504. The position of the transmitting V-UE1 502, for,may be based on the expected location of the V-UE1 502, if received atstage 1A. If the expected location of the V-UE1 502 was not provided,the position of the transmitting V-UE1 502 at the time of broadcast ofthe ranging signal may be determined by the receiving V-UE2 504 based onthe current location of the V-UE1 502 and the current velocity of theV-UE1 502 provided at stage 1A and the time between receiving themessage at stage 1A and receiving the ranging signal at stage 1B. Forexample, the distance and direction of travel of the transmitting V-UE1502 may be determined based on the current velocity (assuming thevelocity does not change significantly) and the amount of time betweentransmission of the first message at stage 1A and the ranging signal atstage 1B. The current location of the transmitting V-UE1 502 at the timeof broadcasting the first message at stage 1B may be updated by thereceiving V-UE2 504 based on the determined distance and direction oftravel of the transmitting V-UE1 502.

Additional sequences of multi-phase signaling for ranging may bebroadcast by the V-UE1 502, e.g., illustrated as stages 3A, 3B, and 3C,e.g., during a periodic group phase, which may have a periodicity of 100msec. for instance. At stage 3A, similar to stage 1A, the transmittingV-UE1 502 broadcasts a first message that includes one or more ofranging information including the source ID, location information forthe V-UE1 502, and the expected time of the broadcast of the rangingsignal, e.g., if the PRS broadcast is on a licensed spectrum, or acombination thereof. The broadcast first message may be received by anynearby entity, such as V-UE2 504, V-UE3 506, and V-UE4 508.

At stage 3B, the transmitting V-UE1 502 broadcasts the ranging signal,which may be a PRS signal and may include the source ID and a sequenceID, e.g., identifying the sequence of multi-phase signaling from theV-UE1 502 and distinguishing the present sequence from, e.g., theprevious sequence of stages 1A, 1B, and 1C. The broadcast ranging signalmay be received by any nearby entity, such as V-UE2 504, V-UE3 506, andV-UE4 508, which determines the time of arrival of the ranging signal.

At stage 3C, the transmitting V-UE1 502 broadcasts, in a second message,additional ranging information including clock error information, thetime of the broadcast of the ranging signal (at stage 1B), e.g., if thePRS broadcast was on an unlicensed spectrum, or a combination thereof.The broadcast second message may be received by any nearby entity, suchas V-UE2 504, V-UE3 506, and V-UE4 508.

At stage 4, a V-UE2 504 may use the broadcast second sequence ofsignaling received at stages 3A, 3B, and 3C, to determine the rangebetween the V-UE2 504 and the transmitting V-UE1 502 and the position ofthe receiving V-UE2 504, e.g., as discussed at stage 2. The determinedrange may be adjusted based on the clock error as received from thetransmitting V-UE1 502 and/or measured by the receiving V-UE2 504.

At stage 5, the V-UE2 504 receives a sequences of multi-phase signalingfor ranging broadcast by the V-UE3 506. The multi-phase signalingsequence at stage 5 may include three separate stages, similar to stages1A, 1B, and 1C, but specific for transmitting V-UE3 506.

At stage 6, the V-UE2 504 may use the broadcast sequence of signalingreceived at stage 5 to determine the range between the V-UE2 504 and thetransmitting V-UE3 506, similar to the discussion at stages 2 and 4. Insome implementations, the V-UE2 504 may also determine an estimatedposition of the receiving V-UE2 504 based on the ranges and knownpositions of V-UE1 502 (e.g., determined at stages 2 and 4) and V-UE3506 (determined at stage 6). Additionally, the position estimate may beat least partially based on knowledge of the location of the road andlocal geography, for example, eliminating positions that are notprobably or possible for the receiving V-UE2 504.

At stage 7, the V-UE2 504 receives a sequences of multi-phase signalingfor ranging broadcast by the V-UE4 508. The multi-phase signalingsequence at stage 7 may include three separate stages, similar to stages1A, 1B, and 1C, but specific for transmitting V-UE4 508.

At stage 8, the V-UE2 504 may use the broadcast sequence of signalingreceived at stage 7 to determine the range between the V-UE2 504 and thetransmitting V-UE4 508, similar to the discussion at stages 2 and 4.

At stage 9, the V-UE2 504 may determine the position of the receivingV-UE2 504, e.g., based on the determined ranges and known positions ofV-UE1 502 (e.g., determined at stages 2 and 4), V-UE3 506 (determined atstage 6), and V-UE4 508 (determined at stage 8). The V-UE2 504, forexample, may determine a position estimate using trilateration. In someimplementations, the V-UE2 504 may further use inertial sensormeasurements and a previously known position, e.g., in a dead reckoningprocess, to assist in determining the present position. Additionally,the position estimate may be at least partially based on knowledge ofthe location of the road and local geography, for example, eliminatingpositions that are not probably or possible for the receiving V-UE2 504.

At stage 10, the V-UE2 504 may determine clock error information, e.g.,based on ranging sequences received from other V-UEs, and the positionof the V-UE2 504, e.g., determined at stage 9. For example, the V-UE2504 may compare its determined position, e.g., as determined at stage 9and/or determined using other means, such as dead-reckoning or asatellite positioning system (SPS) such as GPS, to estimated positionsbased on received ranging signals. The clock error may be determinedbased on the difference in estimated positions as discussed further inFIG. 7, and a variance in clock error may be determined the change inclock error over repeated measurements. The V-UE2 504 may include theclock error information in the second message of its own multi-phasedranging sequences (not shown in FIG. 5).

FIG. 6 illustrates an environment 600 in which a V-UE 602 determines itsrange to multiple other V-UEs 604, 606, and 608 and its position, e.g.,using procedure shown in FIG. 5. As illustrated, for example, the V-UE602 may determines its range D1 to V-UE 604, which defines a circle 603around V-UE 604 having radius D1. The position of the transmitting V-UE604 at the time of broadcasting the ranging signal is known based on thelocation information included in the first message of the multi-phaseranging sequence, e.g., at stage 1A or stage 3A of FIG. 5. Thus, theposition of the receiving V-UE 602 may be anywhere on the circle 603.With knowledge of the road and local geography, positions that are notprobably or possible for the V-UE 602 may be eliminated, such as anypositions off of the road.

Similarly, the V-UE 602 may determines its range D2 to V-UE 606 usingmulti-phase ranging sequence as discussed in FIG. 5, which defines acircle 605 around V-UE 606 having radius D2. The position of thetransmitting V-UE 606 at the time of broadcasting the ranging signal isknown based on the location information that V-UE 606 included in thefirst message of the multi-phase ranging sequence. Thus, the position ofthe receiving V-UE 602 may be where circle 605 intersects circle 603.With knowledge of the road and local geography, positions that are notprobably or possible for the V-UE 602 may be eliminated, such as theintersection of circle 603 and 605 that occurs off the road.

Similarly, the V-UE 602 may determines its range D3 to V-UE 608 usingmulti-phase ranging sequence as discussed in FIG. 5, which defines acircle 607 around V-UE 608 having radius D3. The position of thetransmitting V-UE 608 at the time of broadcasting the ranging signal isknown based on the location information that V-UE 608 included in thefirst message of the multi-phase ranging sequence. Thus, the position ofthe receiving V-UE 602 may be determined as the intersection of circles603, 605, and 607, e.g., using trilateration.

FIG. 7 illustrates an environment 700 including V-UE 702, V-UE 704, andV-UE 706, and illustrates the determination of clock error by the V-UE702, which V-UE 702 may include in, e.g., the second message (e.g., atstage 1C or 3C of FIG. 5) when V-UE 702 transmits a multi-phase rangingsequence. FIG. 7, for example, illustrates the positions of V-UE 704 andV-UE 706 at a current time T1. FIG. 7 illustrates the position of V-UE702 at a previous time T0 (designated 702 _(T0)). The position of V-UE702 _(T0) at the previous time T0, for example, may have been determinedusing a multi-phase ranging sequence as discussed in FIGS. 5 and 6.

Based on the previous position of V-UE 702 _(T0), the current positionof the V-UE 702 may be estimated using inertial sensors, such asaccelerometers, gyroscopes, magnetometers, and the velocity sensor inthe vehicle (such as a wheel sensor), e.g., in a dead reckoningprocedure, illustrated as inertial position 702 _(INS), which has anuncertainty, as illustrated by the dotted circle around position 702_(INS). The current position of the V-UE 702 may also be estimated basedon determined ranges to the first vehicle V-UE 704 and second vehicleV-UE 706, illustrated as dashed circles around each of V-UE 704 and V-UE706, which produces a ranging position 702 _(Range). In someimplementations, a range to a third vehicle may be used to determine theranging position 702 _(Range). The ranges to V-UE 704 and 706 includeclock errors. If desired, additional estimated positions of the V-UE 702may be determined, e.g., using a GPS sensor. Using the various estimatedpositions, e.g., 702 _(INS) and 702 _(Range), a final estimated positionof the V-UE 702 _(true) may be determined. For example, the confidencelevel of each sensor output that produces the respective positions iscaptured as the standard deviation of each position. The positions maybe combined based on the multiple standard deviations. For example, ifone sensor has a high standard deviation, it indicates that the outputbased on that measurement is noisy and may be given less weight.

The difference 4 between the final estimated position of the V-UE 702_(true) and the estimated position based on ranging, e.g., position 702_(Range) may be used to determine the clock error for the V-UE 702,e.g., by dividing the difference in positions by the speed of light. Bymonitoring the clock error estimation over time, e.g., for two or moretime instances, the variance of the clock error estimation for the V-UE702 may be determined. When the V-UE 702 transmits a multi-phase rangingsequence, the V-UE 702 may provide the clock error information, e.g., inthe second message at stage 1C or 3C shown in FIG. 5.

The receiving V-UE may determine the range to the transmitting V-UE asthe difference between the time of broadcast of the PRS signal (asindicated by the transmitting V-UE) and the time of arrival of the PRSsignal (as measured by the receiving V-UE). The receiving V-UE maycorrect the range using the clock error estimation provided by thetransmitting V-UE in the second message, e.g., at stage 1C of FIG. 5.For example, the receiving V-UE may alter (increase or decrease, asappropriate) by the clock error estimation provided by the transmittingV-UE.

FIG. 8 shows a schematic block diagram illustrating certain exemplaryfeatures of a vehicle user equipment (V-UE) 800, which may be UE in avehicle, such as described in reference to FIGS. 1-7. The V-UE 800 maybe configured to control the automated driving of a vehicle 102,including using a multi-phase ranging sequence for ranging andpositioning, as discussed herein. The V-UE 800 may include a vehicleinterface 805 with which commands are provided to the vehicle forautomated driving and sensory input, including speed and acceleration,may be provided from the vehicle to V-UE 800. The V-UE 800 may, forexample, include one or more processors 802, memory 804, an inertialmeasurement unit (IMU) 807 that may include, e.g., an accelerometer,gyroscope, magnetometers, etc., which may be used to detect the motionor one or more motion characteristics of the vehicle, a satellitepositioning system (SPS) receiver 809 to determine, e.g., a GPSposition, and an external interface including, e.g., a Wireless WideArea Network (WWAN) transceiver 810, and a Wireless Local Area Network(WLAN) transceiver 814, which may be operatively coupled with one ormore connections 806 (e.g., buses, lines, fibers, links, etc.) tonon-transitory computer readable medium 820 and memory 804. The V-UE 800may further include additional items, which are not shown, such as auser interface that may include e.g., a display, a keypad or other inputdevice, such as virtual keypad on the display, through which a user mayinterface with the user device. In certain example implementations, allor part of V-UE 800 may take the form of a chipset, and/or the like.Transceiver 810 may be, e.g., a cellular transceiver, that is configuredto transmit and receive inter-vehicle communications in the wirelessnetwork, as illustrated in FIG. 1. The transceiver 810 may include atransmitter 811 enabled to transmit one or more signals over one or moretypes of wireless communication networks and a receiver 812 to receiveone or more signals transmitted over the one or more types of wirelesscommunication networks. Transceiver 814 may be, e.g., a short rangetransceiver, and may be configured to transmit and receive inter-vehiclecommunications in the wireless network, as illustrated in FIG. 1. Thetransceiver 814 may include a transmitter 815 enabled to transmit one ormore signals, including PRS and ITS messages, over one or more types ofwireless communication networks and a receiver 816 to receive one ormore signals, e.g., including PRS and ITS messages, transmitted over theone or more types of wireless communication networks. The transceivers810 and 814 enable the V-UE 800 to communicate with transportationentities using D2D communication links, such as DSRC, C-V2X, or 5G NR.

In some embodiments, V-UE 800 may include antenna 809, which may beinternal or external. The antenna 809 may be used to transmit and/orreceive signals processed by transceiver 810 and/or transceiver 814. Insome embodiments, antenna 809 may be coupled to transceiver 810 and/ortransceiver 814. In some embodiments, measurements of signals received(transmitted) by V-UE 800 may be performed at the point of connection ofthe antenna 809 and transceiver 810 and/or transceiver 814. For example,the measurement point of reference for received (transmitted) RF signalmeasurements may be an input (output) terminal of the receivers 812, 816(transmitters 811, 815) and an output (input) terminal of the antenna809. In a V-UE 800 with multiple antennas 809 or antenna arrays, theantenna connector may be viewed as a virtual point representing theaggregate output (input) of multiple antennas.

The one or more processors 802 may be implemented using a combination ofhardware, firmware, and software. For example, the one or moreprocessors 802 may be configured to perform the functions discussedherein by implementing one or more instructions or program code 808 on anon-transitory computer readable medium, such as medium 820 and/ormemory 804. In some embodiments, the one or more processors 802 mayrepresent one or more circuits configurable to perform at least aportion of a data signal computing procedure or process related to theoperation of V-UE 800.

The medium 820 and/or memory 804 may store instructions or program code808 that contain executable code or software instructions that whenexecuted by the one or more processors 802 cause the one or moreprocessors 802 to operate as a special purpose computer programmed toperform the techniques disclosed herein. As illustrated in V-UE 800, themedium 820 and/or memory 804 may include one or more components ormodules that may be implemented by the one or more processors 802 toperform the methodologies described herein. While the components ormodules are illustrated as software in medium 820 that is executable bythe one or more processors 802, it should be understood that thecomponents or modules may be stored in memory 804 or may be dedicatedhardware either in the one or more processors 802 or off the processors.

A number of software modules and data tables may reside in the medium820 and/or memory 804 and be utilized by the one or more processors 802in order to manage both communications and the functionality describedherein. It should be appreciated that the organization of the contentsof the medium 820 and/or memory 804 as shown in V-UE 800 is merelyexemplary, and as such the functionality of the modules and/or datastructures may be combined, separated, and/or be structured in differentways depending upon the implementation of the V-UE 800.

The medium 820 and/or memory 804 may include an ITS message module 822that when implemented by the one or more processors 802 configures theone or more processors 802 to generate and broadcast and to receive ITSmessages via the transceiver 814. The generated or received ITSmessages, for example, may include a source identifier identifying theV-UE, location information for the V-UE, and an time of broadcast of theranging signal. The location information, for example, may be a currentlocation, e.g., determined using a multi-phase ranging sequence forranging and positioning, and a current velocity, e.g., determined basedon the IMU 807 and/or vehicle interface 805, or the expected location atthe expected time of broadcast of a ranging signal, e.g., determinedbased on the current location and velocity and the time until broadcastof the ranging signal. The generated or received ITS messages mayinclude clock error information, such as the clock drift, clock bias,variance in the clock drift and clock bias, and the time of broadcast ofthe ranging signal. The information related to the ranging signal mayadditionally be configured to include a sequence identifier identifyinga ranging signal sequence that includes the first message, a rangingsignal, and a second message.

The medium 820 and/or memory 804 may include a ranging signal module 824that when implemented by the one or more processors 802 configures theone or more processors 802 to broadcast or receive, via the via thetransceiver 814, a ranging signal. The ranging signal, for example, maybe a PRS signal as discussed herein. The ranging signal may beconfigured to include the source identifier. In some implementations,the ranging signal may be further configured to include the sequenceidentifier. The one or more processors 802, for example, may beconfigured to measure the time of arrival of a received ranging signal.

The medium 820 and/or memory 804 may include a range module 826 thatwhen implemented by the one or more processors 802 configures the one ormore processors 802 to determine a range to a broadcasting transmitter,e.g., based on the time of arrival of a received ranging signal and theexpected time of transmission of the ranging signal, e.g., as broadcastin a preceding ITS message, which may be associated with the rangingsignal using the source ID and sequence ID (if present). The one or moreprocessors 802 may be configured to correct the expected time oftransmission (or time of arrival) based on the clock error informationreceived in an ITS message, which may be associated with the rangingsignal using the source ID and sequence ID (if present). The one or moreprocessors 802, for example, may be configured to divide the differencebetween the time of arrival and the expected time of transmission by thespeed of the signal (i.e., the speed of light), to determine the rangeto the broadcasting V-UE.

The medium 820 and/or memory 804 may include a position module 828 thatwhen implemented by the one or more processors 802 configures the one ormore processors 802 to determine a position of the V-UE 800, e.g., basedon one or more ranges to broadcasting V-UEs and their locationinformation using trilateration or other appropriate techniquesdiscussed herein. For example, the expected location may be broadcast byin the ITS message, or a current location and current velocity may bebroadcast in the ITS message, from which the location at the time ofbroadcast of the ranging signal may be determined, e.g. based on thetime between receipt of the ITS message and the ranging signal. The atleast one processor 802 may be configured to use sensor measurementsfrom IMU 807 to assist in position determination.

The medium 820 and/or memory 804 may include a clock error module 830that when implemented by the one or more processors 802 configures theone or more processors 802 to determine clock error information for theV-UE 800, e.g., based on estimated positions determined using receivedranging signal and a position estimate based on sensor measurements fromIMU 807, e.g. based on dead reckoning, as discussed herein.

The methodologies described herein may be implemented by various meansdepending upon the application. For example, these methodologies may beimplemented in hardware, firmware, software, or any combination thereof.For a hardware implementation, the one or more processors 802 may beimplemented within one or more application specific integrated circuits(ASICs), digital signal processors (DSPs), digital signal processingdevices (DSPDs), programmable logic devices (PLDs), field programmablegate arrays (FPGAs), processors, controllers, micro-controllers,microprocessors, electronic devices, other electronic units designed toperform the functions described herein, or a combination thereof.

For a firmware and/or software implementation, the methodologies may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. Any machine readable mediumtangibly embodying instructions may be used in implementing themethodologies described herein. For example, software codes may bestored in a non-transitory computer readable medium 820 or memory 804that is connected to and executed by the one or more processors 802.Memory may be implemented within the one or more processors or externalto the one or more processors. As used herein the term “memory” refersto any type of long term, short term, volatile, nonvolatile, or othermemory and is not to be limited to any particular type of memory ornumber of memories, or type of media upon which memory is stored.

If implemented in firmware and/or software, the functions may be storedas one or more instructions or program code 808 on a non-transitorycomputer readable medium, such as medium 820 and/or memory 804. Examplesinclude computer readable media encoded with a data structure andcomputer readable media encoded with a computer program 808. Forexample, the non-transitory computer readable medium including programcode 808 stored thereon may include program code 808 to supporttransmission and reception of multi-phase ranging sequence fordetermining a range and position in a manner consistent with disclosedembodiments. Non-transitory computer readable medium 820 includesphysical computer storage media. A storage medium may be any availablemedium that can be accessed by a computer. By way of example, and notlimitation, such non-transitory computer readable media can compriseRAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic diskstorage or other magnetic storage devices, or any other medium that canbe used to store desired program code 808 in the form of instructions ordata structures and that can be accessed by a computer; disk and disc,as used herein, includes compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk and Blu-ray disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer readable media.

In addition to storage on computer readable medium 820, instructionsand/or data may be provided as signals on transmission media included ina communication apparatus. For example, a communication apparatus mayinclude a transceiver 810 having signals indicative of instructions anddata. The instructions and data are configured to cause one or moreprocessors to implement the functions outlined in the claims. That is,the communication apparatus includes transmission media with signalsindicative of information to perform disclosed functions.

Memory 804 may represent any data storage mechanism. Memory 804 mayinclude, for example, a primary memory and/or a secondary memory.Primary memory may include, for example, a random access memory, readonly memory, etc. While illustrated in this example as being separatefrom one or more processors 802, it should be understood that all orpart of a primary memory may be provided within or otherwiseco-located/coupled with the one or more processors 802. Secondary memorymay include, for example, the same or similar type of memory as primarymemory and/or one or more data storage devices or systems, such as, forexample, a disk drive, an optical disc drive, a tape drive, a solidstate memory drive, etc.

In certain implementations, secondary memory may be operativelyreceptive of, or otherwise configurable to couple to a non-transitorycomputer readable medium 820. As such, in certain exampleimplementations, the methods and/or apparatuses presented herein maytake the form in whole or part of a computer readable medium 820 thatmay include computer implementable code 808 stored thereon, which ifexecuted by one or more processors 802 may be operatively enabled toperform all or portions of the example operations as described herein.Computer readable medium 820 may be a part of memory 804.

FIG. 9 is a flow chart 900 illustrating ranging between vehiclesperformed by a vehicle based user equipment (V-UE), such as V-UE 102. Atblock 902, one or more messages are broadcast with information relatedto a ranging signal, the information comprising a source identifieridentifying the V-UE, location information for the V-UE, clock errorinformation for the V-UE, and a time of broadcast of a ranging signal,the one or more messages broadcast before, or after, or both before andafter broadcasting the ranging signal, such as discussed at stages 1A,1C, 3A or 3C of FIG. 5. In some implementations, the one or moremessages with the information related to the ranging signal may bebroadcast in an Intelligent Transport System (ITS) spectrum. In oneexample, the location information may include, for example, a locationof the V-UE and a velocity of the V-UE when broadcasting the one or moremessages. In another example, the location information may be anexpected location of the V-UE at the time of broadcast of the rangingsignal. In some implementations, the information related to the rangingsignal may additionally include a sequence identifier identifying withrespect to other ranging signal sequences a ranging signal sequence thatincludes the one or more messages and the ranging signal. The one ormore messages, for example, may be broadcast on a licensed or unlicensedspectrum. In some implementations, the clock error information for theV-UE may be the clock drift and clock bias, while in otherimplementations, the clock drift information may be a variance in theclock drift and clock bias. In some implementations, the second messagemay include the source identifier. In some implementations, the secondmessage may further include the sequence identifier. The second message,for example, may be broadcast on a licensed spectrum. A means forbroadcasting one or more messages with information related to a rangingsignal, the information comprising a source identifier identifying theV-UE, location information for the V-UE, clock error information for theV-UE, and a time of broadcast of a ranging signal, the one or moremessages broadcast before, or after, or both before and afterbroadcasting the ranging signal may be, e.g., the transceiver 814 andthe one or more processors 802 with dedicated hardware or implementingexecutable code or software instructions in memory 804 and/or medium820, such as the ITS message module 822.

At block 904, the ranging signal is broadcast, the ranging signalcomprising the source identifier, e.g., as discussed at stages 1B and 3Bof FIG. 5. In some implementations, the ranging signal may be furtherinclude the sequence identifier. In some implementations, a waveform ofthe ranging signal is associated with the source identifier. The rangingsignal, for example, may be broadcast on a licensed or unlicensedspectrum. A means for broadcasting the ranging signal, the rangingsignal comprising the source identifier may be, e.g., the transceiver814 and the one or more processors 802 with dedicated hardware orimplementing executable code or software instructions in memory 804and/or medium 820, such as the ranging signal module 824.

In some implementations, the one or more messages may be a first messagebroadcast before broadcasting the ranging signal, the first messagecomprising the source identifier identifying the V-UE and the locationinformation for the V-UE, and a second message broadcast afterbroadcasting the ranging signal, the second message comprising the clockerror information for the V-UE, wherein the time of broadcast of theranging signal is provided in one of the first message before theranging signal is broadcast and the second message after the rangingsignal is broadcast

In some implementations, the method may further include receivingranging signals from at least one other V-UE, e.g., as discussed atstages 1A, 1B, 1C, 3A, 3B, 3C, 5, and 7 in FIG. 5. The clock errorinformation may be determined for the V-UE based on the ranging signalsfrom the at least one other V-UE, e.g., as discussed at stage 10 of FIG.5. In some implementation, the V-UE may determine the clock errorinformation based on a difference between determine one or moreestimated positions based on ranging signals and an estimated positionbased on inertial sensors. A means for receiving ranging signals from atleast one other V-UE may be, e.g., the transceiver 814 and the one ormore processors 802 with dedicated hardware or implementing executablecode or software instructions in memory 804 and/or medium 820, such asthe ITS message module 822, and ranging signal module 824. A means fordetermining the clock error information for the V-UE based on theranging signals from the at least one other V-UE may be, e.g., thetransceiver 814 and the one or more processors 802 with dedicatedhardware or implementing executable code or software instructions inmemory 804 and/or medium 820, such as the range module 826, positionmodule 828, and the clock error module 830.

In some implementations, the first message, the ranging signal, and thesecond message may be a first ranging signal sequence, and the methodmay include broadcasting multiple ranging signal sequences at differenttime instances, e.g., as discussed at stages 3A, 3B, and 3C of FIG. 5. Ameans for broadcasting multiple ranging signal sequences at differenttime instances may be, e.g., the transceiver 814 and the one or moreprocessors 802 with dedicated hardware or implementing executable codeor software instructions in memory 804 and/or medium 820, such as theITS message module 822 and the ranging signal module 824.

FIG. 10 is a flow chart 1000 illustrating ranging between vehiclesperformed by a first vehicle based user equipment (V-UE), such as V-UE102. At block 1002, one or more messages broadcast by a second V-UE arereceived, the one or more messages comprising information related to aranging signal to be broadcast by the second V-UE, the informationcomprising a source identifier identifying the second V-UE, locationinformation for the second V-UE, clock error information for the secondV-UE, and a time of broadcast of a ranging signal, the one or moremessages is received before, or after, or both before and afterreceiving the ranging signal, such as discussed at stages 1A, 1C, 3A, or3C of FIG. 5. In some implementations, the one or more messages with theinformation related to the ranging signal may be received in anIntelligent Transport System (ITS) spectrum. In one example, thelocation information may include, for example, a location of the V-UEand a velocity of the V-UE when broadcasting the one or more messages.In another example, the location information may be an expected locationof the V-UE at the time of broadcast of the ranging signal. In someimplementations, the information related to the ranging signal mayadditionally include a sequence identifier identifying with respect toother ranging signal sequences a ranging signal sequence that includesthe one or more messages and the ranging signal. The one or moremessages, for example, may be received on a licensed spectrum orunlicensed spectrum. In some implementations, the second message may bereceived in an Intelligent Transport System (ITS) spectrum. In someimplementations, the clock error information for the V-UE may be theclock drift and clock bias, while in other implementations, the clockdrift information may be a variance in the clock drift and clock bias.In some implementations, the second message may include the sourceidentifier. In some implementations, the second message may furtherinclude the sequence identifier. The second message, for example, may bereceived on a licensed spectrum. A means for receiving one or moremessages broadcast by a second V-UE, the one or more messages comprisinginformation related to a ranging signal to be broadcast by the secondV-UE, the information comprising a source identifier identifying thesecond V-UE, location information for the second V-UE, clock errorinformation for the second V-UE, and a time of broadcast of a rangingsignal, the one or more messages is received before, or after, or bothbefore and after receiving the ranging signal may be, e.g., thetransceiver 814 and the one or more processors 802 with dedicatedhardware or implementing executable code or software instructions inmemory 804 and/or medium 820, such as the ITS message module 822.

At block 1004, the ranging signal broadcast by the second V-UE may bereceived, the ranging signal comprising the source identifier, e.g., asdiscussed at stages 1B and 3B of FIG. 5. In some implementations, theranging signal may be further include the sequence identifier. Theranging signal, for example, may be received on a licensed or unlicensedspectrum. In one implementation, a waveform of the ranging signal isassociated with the source identifier. A means for receiving the rangingsignal broadcast by the second V-UE, the ranging signal comprising thesource identifier may be, e.g., the transceiver 814 and the one or moreprocessors 802 with dedicated hardware or implementing executable codeor software instructions in memory 804 and/or medium 820, such as theranging signal module 824.

At block 1006, a range to the second V-UE is determined based on theinformation related to the ranging signal, the ranging signal, and theclock error information received from the second V-UE, e.g., asdiscussed at stages 2 and 4 of FIG. 5. In one implementation, the rangemay be determined based on a measured time of arrival of the rangingsignal and the expected time of transmission of the ranging signal,which may be corrected using the clock error information. In oneimplementation, the difference between the time of arrival and theexpected time of transmission may be divided by the speed of the lightto determine the range. A means for determining a range to the secondV-UE based on the information related to the ranging signal, the rangingsignal, and the clock error information received from the second V-UEmay be, e.g., the one or more processors 802 with dedicated hardware orimplementing executable code or software instructions in memory 804and/or medium 820, such as the range module 826.

In some implementations, the one or more messages and the ranging signalmay be a first ranging signal sequence, and the method may includereceiving multiple ranging signal sequences at different time instances,e.g., as discussed at stages 3A, 3B, and 3C of FIG. 5. A means forreceiving multiple ranging signal sequences at different time instancesmay be, e.g., the transceiver 814 and the one or more processors 802with dedicated hardware or implementing executable code or softwareinstructions in memory 804 and/or medium 820, such as the ITS messagemodule 822 and the ranging signal module 824.

In some implementations, the one or more messages and the ranging signalmay be a first ranging signal sequence. The method may further includereceiving a second ranging signal sequences from a third V-UE includingat least a location of the third V-UE and a velocity of the third V-UE,and determining a range to the third V-UE, e.g., as discussed at stages5 and 6 of FIG. 5. A means for receiving a second ranging signalsequences from a third V-UE including at least a location of the thirdV-UE and a velocity of the third V-UE, and determining a range to thethird V-UE may be, e.g., the transceiver 814 and the one or moreprocessors 802 with dedicated hardware or implementing executable codeor software instructions in memory 804 and/or medium 820, such as theITS message module 822 and the ranging signal module 824, and the rangemodule 826. The method may further include receiving a third rangingsignal sequences from a fourth V-UE including at least a location of thefourth V-UE and a velocity of the fourth V-UE and determining a range tothe fourth V-UE, e.g., as discussed at stages 7 and 8 of FIG. 5. A meanfor receiving a third ranging signal sequences from a fourth V-UEincluding at least a location of the fourth V-UE and a velocity of thefourth V-UE and determining a range to the fourth V-UE may be, e.g., thetransceiver 814 and the one or more processors 802 with dedicatedhardware or implementing executable code or software instructions inmemory 804 and/or medium 820, such as the ITS message module 822 and theranging signal module 824, and the range module 826. The method mayfurther include determining a location of the first V-UE based on therange to the second V-UE, the range to the third V-UE, and the range tothe fourth V-UE, and locations of the second V-UE, the third V-UE, andthe fourth V-UE and velocities of the second V-UE, the third V-UE, andthe fourth V-UE, e.g., as discussed at stage 9 of FIG. 5. A means fordetermining a location of the first V-UE based on the range to thesecond V-UE, the range to the third V-UE, and the range to the fourthV-UE, and locations of the second V-UE, the third V-UE, and the fourthV-UE and velocities of the second V-UE, the third V-UE, and the fourthV-UE may be, e.g., the one or more processors 802 with dedicatedhardware or implementing executable code or software instructions inmemory 804 and/or medium 820, such as the position module 828.

Reference throughout this specification to “one example”, “an example”,“certain examples”, or “exemplary implementation” means that aparticular feature, structure, or characteristic described in connectionwith the feature and/or example may be included in at least one featureand/or example of claimed subject matter. Thus, the appearances of thephrase “in one example”, “an example”, “in certain examples” or “incertain implementations” or other like phrases in various placesthroughout this specification are not necessarily all referring to thesame feature, example, and/or limitation. Furthermore, the particularfeatures, structures, or characteristics may be combined in one or moreexamples and/or features.

Some portions of the detailed description included herein are presentedin terms of algorithms or symbolic representations of operations onbinary digital signals stored within a memory of a specific apparatus orspecial purpose computing device or platform. In the context of thisparticular specification, the term specific apparatus or the likeincludes a general purpose computer once it is programmed to performparticular operations pursuant to instructions from program software.Algorithmic descriptions or symbolic representations are examples oftechniques used by those of ordinary skill in the signal processing orrelated arts to convey the substance of their work to others skilled inthe art. An algorithm is here, and generally, is considered to be aself-consistent sequence of operations or similar signal processingleading to a desired result. In this context, operations or processinginvolve physical manipulation of physical quantities. Typically,although not necessarily, such quantities may take the form ofelectrical or magnetic signals capable of being stored, transferred,combined, compared, or otherwise manipulated. It has proven convenientat times, principally for reasons of common usage, to refer to suchsignals as bits, data, values, elements, symbols, characters, terms,numbers, numerals, or the like. It should be understood, however, thatall of these or similar terms are to be associated with appropriatephysical quantities and are merely convenient labels. Unlessspecifically stated otherwise, as apparent from the discussion herein,it is appreciated that throughout this specification discussionsutilizing terms such as “processing,” “computing,” “calculating,”“determining” or the like refer to actions or processes of a specificapparatus, such as a special purpose computer, special purpose computingapparatus or a similar special purpose electronic computing device. Inthe context of this specification, therefore, a special purpose computeror a similar special purpose electronic computing device is capable ofmanipulating or transforming signals, typically represented as physicalelectronic or magnetic quantities within memories, registers, or otherinformation storage devices, transmission devices, or display devices ofthe special purpose computer or similar special purpose electroniccomputing device.

In the preceding detailed description, numerous specific details havebeen set forth to provide a thorough understanding of claimed subjectmatter. However, it will be understood by those skilled in the art thatclaimed subject matter may be practiced without these specific details.In other instances, methods and apparatuses that would be known by oneof ordinary skill have not been described in detail so as not to obscureclaimed subject matter.

The terms, “and”, “or”, and “and/or” as used herein may include avariety of meanings that also are expected to depend at least in partupon the context in which such terms are used. Typically, “or” if usedto associate a list, such as A, B or C, is intended to mean A, B, and C,here used in the inclusive sense, as well as A, B or C, here used in theexclusive sense. In addition, the term “one or more” as used herein maybe used to describe any feature, structure, or characteristic in thesingular or may be used to describe a plurality or some othercombination of features, structures, or characteristics. Though, itshould be noted that this is merely an illustrative example and claimedsubject matter is not limited to this example.

While there has been illustrated and described what are presentlyconsidered to be example features, it will be understood by thoseskilled in the art that various other modifications may be made, andequivalents may be substituted, without departing from claimed subjectmatter. Additionally, many modifications may be made to adapt aparticular situation to the teachings of claimed subject matter withoutdeparting from the central concept described herein.

Therefore, it is intended that claimed subject matter not be limited tothe particular examples disclosed, but that such claimed subject mattermay also include all aspects falling within the scope of appendedclaims, and equivalents thereof.

What is claimed is:
 1. A method of ranging between vehicles performed bya vehicle based user equipment (V-UE), the method comprising:broadcasting one or more messages with information related to a rangingsignal, the information comprising a source identifier identifying theV-UE, location information for the V-UE, clock error information for theV-UE, and a time of broadcast of a ranging signal, the one or moremessages broadcast before, or after, or both before and afterbroadcasting the ranging signal; and broadcasting the ranging signal,the ranging signal comprising the source identifier.
 2. The method ofclaim 1, wherein the one or more messages comprises a first messagebroadcast before broadcasting the ranging signal, the first messagecomprising the source identifier identifying the V-UE and the locationinformation for the V-UE, and a second message broadcast afterbroadcasting the ranging signal, the second message comprising the clockerror information for the V-UE, wherein the time of broadcast of theranging signal is provided in one of the first message before theranging signal is broadcast and the second message after the rangingsignal is broadcast.
 3. The method of claim 1, wherein the one or moremessages with the information related to the ranging signal is broadcastin an Intelligent Transport System (ITS) spectrum and the one or moremessages and the ranging signal are broadcast on a licensed spectrum oran unlicensed spectrum.
 4. The method of claim 1, wherein the locationinformation comprises at least one of a location of the V-UE, a velocityof the V-UE when broadcasting the one or more messages, and an expectedlocation of the V-UE at the time of broadcast of the ranging signal. 5.The method of claim 1, wherein the information related to the rangingsignal further comprises a sequence identifier identifying with respectto other ranging signal sequences a ranging signal sequence comprisingthe one or more messages and the ranging signal, wherein the rangingsignal further comprises the sequence identifier.
 6. The method of claim1, further comprising: receiving ranging signals from at least one otherV-UE; and determining the clock error information for the V-UE based onthe ranging signals from the at least one other V-UE.
 7. The method ofclaim 1, wherein the clock error information for the V-UE comprises aclock drift and clock bias or a variance in the clock drift and clockbias.
 8. The method of claim 1, wherein the one or more messages and theranging signal comprise a first ranging signal sequence, the methodfurther comprising broadcasting multiple ranging signal sequences atdifferent time instances.
 9. The method of claim 1, wherein a waveformof the ranging signal is associated with the source identifier.
 10. Avehicle based user equipment (V-UE) configured for ranging betweenvehicles, comprising: a wireless transceiver configured to receivebroadcast signals from other V-UEs; at least one memory; and at leastone processor coupled to the wireless transceiver and the at least onememory, the at least one processor configured to: broadcast one or moremessages with information related to a ranging signal, the informationcomprising a source identifier identifying the V-UE, locationinformation for the V-UE, clock error information for the V-UE, and atime of broadcast of a ranging signal, the one or more messagesbroadcast before, or after, or both before and after broadcasting theranging signal; and broadcast the ranging signal, the ranging signalcomprising the source identifier.
 11. The V-UE of claim 10, wherein theone or more messages comprises a first message broadcast before theranging signal is broadcast, the first message comprising the sourceidentifier identifying the V-UE and the location information for theV-UE, and a second message broadcast after the ranging signal isbroadcast, the second message comprising the clock error information forthe V-UE, wherein the time of broadcast of the ranging signal isprovided in one of the first message before the ranging signal isbroadcast and the second message after the ranging signal is broadcast.12. The V-UE of claim 10, wherein the one or more messages with theinformation related to the ranging signal is broadcast in an IntelligentTransport System (ITS) spectrum and the one or more messages and theranging signal are broadcast on a licensed spectrum or an unlicensedspectrum.
 13. The V-UE of claim 10, wherein the location informationcomprises at least one of a location of the V-UE, a velocity of the V-UEwhen broadcasting the one or more messages, and an expected location ofthe V-UE at the time of broadcast of the ranging signal.
 14. The V-UE ofclaim 10, wherein the information related to the ranging signal furthercomprises a sequence identifier identifying with respect to otherranging signal sequences a ranging signal sequence comprising the one ormore messages and the ranging signal, wherein the ranging signal furthercomprises the sequence identifier.
 15. The V-UE of claim 10, wherein theat least one processor is further configured to: receive ranging signalsfrom at least one other V-UE; and determine the clock error informationfor the V-UE based on the ranging signals from the at least one otherV-UE.
 16. The V-UE of claim 10, wherein the clock error information forthe V-UE comprises a clock drift and clock bias or a variance in theclock drift and clock bias.
 17. The V-UE of claim 10, wherein the one ormore messages and the ranging signal comprise a first ranging signalsequence, wherein the at least one processor is further configured tobroadcast multiple ranging signal sequences at different time instances.18. The V-UE of claim 10, wherein a waveform of the ranging signal isassociated with the source identifier.
 19. A method of ranging betweenvehicles performed by a first vehicle based user equipment (V-UE), themethod comprising: receiving one or more messages broadcast by a secondV-UE, the one or more messages comprising information related to aranging signal to be broadcast by the second V-UE, the informationcomprising a source identifier identifying the second V-UE, locationinformation for the second V-UE, clock error information for the secondV-UE, and a time of broadcast of a ranging signal, the one or moremessages is received before, or after, or both before and afterreceiving the ranging signal; receiving the ranging signal broadcast bythe second V-UE, the ranging signal comprising the source identifier;and determining a range to the second V-UE based on the informationrelated to the ranging signal, the ranging signal, and the clock errorinformation received from the second V-UE.
 20. The method of claim 19,wherein the one or more messages comprises a first message receivedbefore receiving the ranging signal, the first message comprising thesource identifier identifying the second V-UE and the locationinformation for the second V-UE, and a second message received afterreceiving the ranging signal, the second message comprising the clockerror information for the second V-UE, wherein the time of broadcast ofthe ranging signal is provided in one of the first message before theranging signal is received and the second message after the rangingsignal is received.
 21. The method of claim 19, wherein the one or moremessages with the information related to the ranging signal is broadcastin an Intelligent Transport System (ITS) spectrum and the one or moremessages and the ranging signal are broadcast on a licensed spectrum oran unlicensed spectrum.
 22. The method of claim 19, wherein the locationinformation comprises a at least one of location of the second V-UE, avelocity of the V-UE when broadcasting the one or more messages, and anexpected location of the V-UE at the time of broadcast of the rangingsignal.
 23. The method of claim 19, wherein the information related tothe ranging signal further comprises a sequence identifier identifyingwith respect to other ranging signal sequences a ranging signal sequencecomprising the one or more messages and the ranging signal, wherein theranging signal further comprises the sequence identifier.
 24. The methodof claim 19, wherein the one or more messages and the ranging signalcomprise a first ranging signal sequence, the method further comprisingreceiving multiple ranging signal sequences from the second V-UE atdifferent time instances.
 25. The method of claim 19, wherein the one ormore messages and the ranging signal comprise a first ranging signalsequence, the method further comprising: receiving a second rangingsignal sequences from a third V-UE including at least a location of thethird V-UE and a velocity of the third V-UE, and determining a range tothe third V-UE; receiving a third ranging signal sequences from a fourthV-UE including at least a location of the fourth V-UE and a velocity ofthe fourth V-UE and determining a range to the fourth V-UE; anddetermining a location of the first V-UE based on the range to thesecond V-UE, the range to the third V-UE, and the range to the fourthV-UE, and locations of the second V-UE, the third V-UE, and the fourthV-UE and velocities of the second V-UE, the third V-UE, and the fourthV-UE.
 26. The method of claim 19, wherein a waveform of the rangingsignal is associated with the source identifier.
 27. A first vehiclebased user equipment (V-UE) configured for ranging between vehicles,comprising: a wireless transceiver configured to receive broadcastsignals from other V-UEs; at least one memory; and at least oneprocessor coupled to the wireless transceiver and the at least onememory, the at least one processor configured to: receive one or moremessages broadcast by a second V-UE, the one or more messages comprisinginformation related to a ranging signal to be broadcast by the secondV-UE, the information comprising a source identifier identifying thesecond V-UE, location information for the second V-UE, clock errorinformation for the second V-UE, and a time of broadcast of a rangingsignal, the one or more messages is received before, or after, or bothbefore and after receiving the ranging signal; and receive the rangingsignal broadcast by the second V-UE, the ranging signal comprising thesource identifier; and determine a range to the second V-UE based on theinformation related to the ranging signal, the ranging signal, and theclock error information received from the second V-UE.
 28. The -UE ofclaim 27, wherein the one or more messages comprises a first messagereceived before receiving the ranging signal, the first messagecomprising the source identifier identifying the second V-UE and thelocation information for the second V-UE, and a second message receivedafter receiving the ranging signal, the second message comprising theclock error information for the second V-UE, wherein the time ofbroadcast of the ranging signal is provided in one of the first messagebefore the ranging signal is received and the second message after theranging signal is received.
 29. The V-UE of claim 27, wherein the one ormore messages with the information related to the ranging signal isbroadcast in an Intelligent Transport System (ITS) spectrum and the oneor more messages and the ranging signal are broadcast on a licensedspectrum or an unlicensed spectrum.
 30. The V-UE of claim 27, whereinthe location information comprises at least one of a location of thesecond V-UE, a velocity of the V-UE when broadcasting the one or moremessages, and an expected location of the V-UE at the time of broadcastof the ranging signal.
 31. The V-UE of claim 27, wherein the informationrelated to the ranging signal further comprises a sequence identifieridentifying with respect to other ranging signal sequences a rangingsignal sequence comprising the one or more messages and the rangingsignal, wherein the ranging signal further comprises the sequenceidentifier.
 32. The V-UE of claim 27, wherein the one or more messagesand the ranging signal comprise a first ranging signal sequence, themethod further comprising receiving multiple ranging signal sequencesfrom the second V-UE at different time instances.
 33. The V-UE of claim27, wherein the one or more messages and the ranging signal comprise afirst ranging signal sequence, wherein the at least one processor isfurther configured to: receive a second ranging signal sequences from athird V-UE including at least a location of the third V-UE and avelocity of the third V-UE, and determining a range to the third V-UE;receive a third ranging signal sequences from a fourth V-UE including atleast a location of the fourth V-UE and a velocity of the fourth V-UEand determining a range to the fourth V-UE; and determine a location ofthe first V-UE based on the range to the second V-UE, the range to thethird V-UE, and the range to the fourth V-UE, and locations of thesecond V-UE, the third V-UE, and the fourth V-UE and velocities of thesecond V-UE, the third V-UE, and the fourth V-UE.
 34. The V-UE of claim27, wherein a waveform of the ranging signal is associated with thesource identifier.